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Chapter 64 - Chemical and Biological Warfare Agents: The Role of the Anesthesiologist

David J. Baker

THE NATURE OF CHEMICAL AND BIOLOGICAL WARFARE HAZARDS

Management of exposure to chemical and biological warfare (CBW) agents has long been part of a remote area of clinical practice, confined essentially to military specialists. The World Trade Center attack in September 2001 increased concern about the possible impact of CBW agents released by terrorists on a civilian population. In the past, anesthesiologists have had relatively little to do with planning and advice for CBW casualty management, which has been the domain of specialists in toxicology, microbiology, and occupational health. As a result, CBW casualty management has been dominated by a perception of toxicity and pathogenicity of CBW agents without consideration of the modification

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This chapter addresses the management of casualties who may have been injured or infected after a deliberate exposure to CBW agents from the standpoint of anesthesiologists in all their professional areas of activity, from the provision of emergency life support through management in the intensive care unit. Many anesthesiologists are involved in the management of mass disasters, but a key difference between CBW and conventional mass disaster practice is that medical responders are themselves at risk from the process causing injury. There is an important precedent for the management of CBW incidents from plans for accidental toxic releases. In some countries, anesthesiologists are part of the initial emergency medical response and are trained in the essentials of personal protection and decontamination.^[1] They may also be involved in the initial reception of contaminated casualties at the hospital, particularly when autoreferral occurs.^[2] Casualties with toxic injuries may also have conventional injuries requiring surgery, and this brings a whole new dimension to the management of operative anesthesia that is modified by the effects of a toxic agent. Many of the victims of a CBW attack require immediate and long-term ventilation and other intensive care, an area involving anesthesiologists and intensivists.

In this discussion, the nature and management of CBW agent release is approached first by considering the definition and classification of the agents and then by discussing the properties of key representative agents in terms of pathophysiologic effects. The wide range of potential CBW hazards has been the subject of an exhaustive literature, and it is not my intention to repeat such detailed information here. Instead, key features of representatives of various classes of hazard are discussed from the standpoint of anesthetic and intensive care practice. The practical aspects of the involvement of the anesthesiologist and intensivist in management of CBW agent release are also considered. Their responsibilities comprise management of the patients and safe operation during the incident, including detection of release, protection of responding personnel, and decontamination.

Approaches to the Literature

Many scientific and clinical specialties have been involved in the study of CBW agents for more than a century. The literature is extensive and covers a wide clinical range. Of the specialties involved, toxicology, microbiology, and occupational health have been the most dominant and have imparted their particular influences. In the scientific area, there is a wealth of literature that is easily comprehended by anesthesiologists who have a special interest in synaptic and cellular mechanisms. Much of the literature relevant to CBW agents predates the Medline era and is not readily accessible from this source. Fortunately, many reviews and books exist, particularly in the exhaustively studied area of cholinergic transmission, which make the careful and relevant work of early researchers still relatively easily accessible to modern anesthetists.^{[3] [4] [5] [6] [7] [8] [9]} These sources can be consulted to gain a working background of the nature of CBW agents. Many web sites are devoted to all aspects of toxic release and provide specific technical information.

Evidence-Based Studies

The study of CBW agents in humans has been less extensive than human studies in other areas of clinical medicine. This is understandable because prospective studies that involve exposure of human subjects willingly or otherwise have been strictly controlled or proscribed by international convention. Despite this, there is a large amount of information in the literature from early clinical volunteer studies and from accidental exposures to chemical warfare agents, and many unpublished or inaccessible reports have been carefully reviewed by Marrs and colleagues. ^[7] In the biological warfare field, there are also recent reviews^{[10] [11] [12]} and valuable continuing clinical study in the parallel field of accidental (rather than deliberate) infection together with literature on the development of antimicrobial and antiviral agents, which is of immediate relevance to biological warfare release.

Secrecy

Although considerable information about the pathophysiology and management of CBW cases exists in the open literature, it is likely that far more information is still classified by governments involved in the subject and is not easily accessible.^[7] Nevertheless, there is much historical information available from time-declassified government sources^[13] and from searching the sources provided by the Freedom of Information Act in the United States. Other nongovernmental organizations, such as the Stockholm International Peace Research Institute (SIPRI), have also published extensive information, although this information may have a certain political bias.^[14] By far, the most research on CBW agents was carried out by the Soviet Union during the Cold War, and large amounts of this information remain unpublished. However, Soviet scientists involved in programs such as Mikrobioprom^[15] and the application of genetic engineering to CBW agents did publish many articles on techniques, and these papers can readily be accessed through the databases because the major part of the Soviet program started after signing the 1972 Biological Warfare Treaty,^[16] which led to the discontinuation of biological warfare research by the West.